A5078991971- Quantum Computing Algorithms and Architecture
- Quantum Information and Cryptography
- Quantum and electron transport phenomena
- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Molecular Junctions and Nanostructures
- Molecular spectroscopy and chirality
- Catalysis and Oxidation Reactions
- Physics of Superconductivity and Magnetism
- Neural Networks and Reservoir Computing
- Quantum many-body systems
- Catalytic Processes in Materials Science
- Quantum-Dot Cellular Automata
- Magnetism in coordination complexes
- Advanced NMR Techniques and Applications
- Parallel Computing and Optimization Techniques
- Electron Spin Resonance Studies
- Photochemistry and Electron Transfer Studies
- Machine Learning in Materials Science
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum, superfluid, helium dynamics
- Computational Drug Discovery Methods
- Electrocatalysts for Energy Conversion
- Magnetic properties of thin films
- Inorganic Fluorides and Related Compounds
Virginia Tech
2016-2025
University of California, Berkeley
2011-2015
Lawrence Berkeley National Laboratory
2013-2014
Center for Theoretical Biological Physics
2014
Indiana University Bloomington
2007-2012
Indiana University
2010
A summary of the technical advances that are incorporated in fourth major release Q-Chem quantum chemistry program is provided, covering approximately last seven years. These include developments density functional theory methods and algorithms, nuclear magnetic resonance (NMR) property evaluation, coupled cluster perturbation theories, for electronically excited open-shell species, tools treating extended environments, algorithms walking on potential surfaces, analysis tools, energy...
Quantum simulation of chemical systems is one the most promising near-term applications quantum computers. The variational eigensolver, a leading algorithm for molecular simulations on hardware, has serious limitation in that it typically relies pre-selected wavefunction ansatz results approximate wavefunctions and energies. Here we present an arbitrarily accurate instead fixing upfront, this grows systematically operator at time way dictated by molecule being simulated. This generates with...
The resources required to run a high-accuracy variational quantum eigensolver algorithm with dynamically created ansatz are quantified and reduced significantly, easing the simulation of many-body systems.
The variational quantum eigensolver is one of the most promising approaches for performing chemistry simulations using noisy intermediate-scale (NISQ) processors. efficiency this algorithm depends crucially on ability to prepare multi-qubit trial states processor that either include, or at least closely approximate, actual energy eigenstates problem being simulated while avoiding have little overlap with them. Symmetries play a central role in determining best states. Here, we present...
The quantum approximate optimization algorithm (QAOA) is a hybrid variational quantum-classical that solves combinatorial problems. While there evidence suggesting the fixed form of standard QAOA Ansatz not optimal, no systematic approach for finding better Ans\"atze. We address this problem by developing an iterative version tailored, and which can also be adapted to specific hardware constraints. simulate on class Max-Cut graph problems show it converges much faster than QAOA, while...
Abstract Variational quantum eigensolvers (VQEs) represent a powerful class of hybrid quantum-classical algorithms for computing molecular energies. Various numerical issues exist these methods, however, including barren plateaus and large numbers local minima. In this work, we consider the Adaptive, Problem-Tailored Quantum Eiegensolver (ADAPT-VQE) ansätze, examine how they are impacted by We find that while ADAPT-VQE does not remove minima, gradient-informed, one-operator-at-a-time circuit...
We present a new extrapolated fragment-based approach, termed molecules-in-molecules (MIM), for accurate energy calculations on large molecules. In this method, we use multilevel partitioning approach coupled with electronic structure studies at multiple levels of theory to provide hierarchical strategy systematically improving the computed results. particular, generalized hybrid expression, similar in spirit that popular ONIOM methodology, can be combined easily any fragmentation procedure....
A common approach to approximating the full electronic energy of a molecular system is first divide into nonoverlapping (disjoint) fragments and then compute two-body or three-body fragment-fragment interactions using many-body expansion. In this paper, we demonstrate that, by set which overlap with each other, expansion converges much faster than fragments. new hierarchical fragmentation scheme therefore proposed generalizes expressions describes simple procedure for generating overlapping...
The variational quantum eigensolver (VQE) has emerged as one of the most promising near-term algorithms that can be used to simulate many-body systems such molecular electronic structures. Serving an attractive ansatz in VQE algorithm, unitary coupled cluster (UCC) theory seen a renewed interest recent literature. However, unlike original classical UCC theory, implementation on computer requires finite-order Suzuki-Trotter decomposition separate exponentials large sum Pauli operators. While...
Abstract The variational quantum eigensolver is currently the flagship algorithm for solving electronic structure problems on near-term computers. involves implementing a sequence of parameterized gates hardware to generate target state, and then measuring molecular energy. Due finite coherence times gate errors, number that can be implemented remains limited. In this work, we propose an alternative where device-level pulse shapes are variationally optimized state preparation rather than...
Near-term quantum computers are expected to facilitate material and chemical research through accurate molecular simulations. Several developments have already shown that ground-state energies for small molecules can be evaluated on present-day devices. Although electronically excited states play a vital role in processes applications, the search reliable practical approach routine excited-state calculations near-term devices is ongoing. Inspired by methods developed unitary coupled-cluster...
Adaptive quantum variational algorithms are particularly promising for simulating strongly correlated systems on near-term hardware, but they not yet viable due, in large part, to the severe coherence time limitations current devices. In this paper, we introduce an algorithm called TETRIS-ADAPT-VQE (tiling efficient trial circuits with rotations implemented simultaneously adaptive derivative-assembled problem-tailored eigensolver), which iteratively builds up a few operators at way dictated...
We provide a simple procedure for using inexpensive ab initio calculations to compute exchange coupling constants, JAB, multiradical molecules containing both an arbitrary number of radical sites and unpaired electrons. For system comprised 2M electrons, one needs only states having the Ŝz quantum M – 1. Conveniently, these are precisely that accessed by family single spin–flip methods. Building effective Hamiltonian with allows extract all JAB constants in molecule. Unlike approaches based...
We present a simple approach for orbital space partitioning to be employed in the projection-based embedding theory developed by Goodpaster and co-workers [ Manby et al. J. Chem. Theory Comput. 2012 , 8 2564 ]. Once atoms are assigned desired subspaces, molecular orbitals projected onto atomic centered on active then singular value decomposed. The right vectors used rotate initial orbitals, taking largest gap values spectrum define most suitable partition of occupied space. This scheme is...
Selected configuration interaction (SCI) methods are currently enjoying a resurgence due to several recent developments which improve either the overall computational efficiency or compactness of resulting SCI vector. These advances have made it possible get full CI (FCI) quality results for much larger orbital active spaces, compared conventional approaches. However, starting assumption that FCI vector has only small number significant Slater determinants, becomes intractable systems with...
Accurate modeling of the response molecular systems to an external electromagnetic field is challenging on classical computers, especially in regime strong electronic correlation. In this article, we develop a quantum linear (qLR) theory calculate properties near-term computers. Inspired by recently developed variants counterpart equation motion (qEOM) theory, qLR formalism employs "killer condition" satisfying excitation operator manifolds that offer number theoretical advantages along with...
Quantum simulation of strongly correlated systems is potentially the most feasible useful application near-term quantum computers. Minimizing computational resources crucial to achieving this goal. A promising class algorithms for purpose consists variational eigensolvers (VQEs). Among these, problem-tailored versions such as ADAPT-VQE that build ans\"atze step by from a predefined operator pool perform particularly well in terms circuit depths and parameter counts. However, improved...
An investigation of the performance Gaussian-4 (G4) methods for prediction 3d transition metal thermochemistry is presented. Using recently developed G3Large basis sets atoms Sc-Zn, G4 and G4(MP2) with scalar relativistic effects included are evaluated on a test set 20 enthalpies formation metal-containing molecules. The method found to perform significantly better than method. fails due poor convergence Møller-Plesset perturbation theory at fourth-order in one case. overall error 2.84...
In this paper, we report the development, implementation, and assessment of a novel method for describing strongly correlated systems, spin–flip non-orthogonal configuration interaction (SF-NOCI). The wavefunction is defined to be linear combination independently relaxed Slater determinants obtained from all possible spin–flipping excitations within localized orbital active-space, typically taken singly occupied orbitals high-spin ROHF wavefunction. constrained optimization each CI basis...
We highlight a simple strategy for computing the magnetic coupling constants, J, complex containing two multiradical centers. On assumption that system follows Heisenberg Hamiltonian physics, J is obtained from spin-flip electronic structure calculation where only single electron excited (and spin-flipped), reference with maximum Ŝz, M, to M - 1 manifold, regardless of number unpaired electrons, 2M, on radical In an active space picture involving 2M orbitals, one β required, together α hole....
We present a modification of the recently developed Restricted Active Space with n Spin Flips method (RAS-nSF), which provides significant efficiency advantages. In RAS-nSF configuration interaction wave function, an arbitrary number spin-flips are performed within orbital active space (often simply singly occupied orbitals), state-specific relaxation being described by single excitations into and out (termed hole particle states, respectively). As states dominates cost calculation, we...
The quantum approximate optimization algorithm (QAOA) is a hybrid variational quantum-classical that solves combinatorial problems. While there evidence suggesting the fixed form of standard QAOA ansatz not optimal, no systematic approach for finding better ans\"atze. We address this problem by developing an iterative version problem-tailored, and which can also be adapted to specific hardware constraints. simulate on class Max-Cut graph problems show it converges much faster than QAOA,...
Several quantum many-body models in one dimension possess exact solutions via the Bethe ansatz method, which has been highly successful for understanding their behavior. Nevertheless, there remain physical properties of such analytic results are unavailable and also not well described by approximate numerical methods. Preparing eigenstates directly on a computer would allow straightforward extraction these quantities measurement. We present algorithm preparing spin-1/2 XXZ spin chain that...
One of the most promising applications noisy intermediate-scale quantum computers is simulation molecular Hamiltonians using variational eigensolver. We show that encoding symmetries simulated Hamiltonian in VQE ansatz reduces both classical and resources compared to other, widely available ansatze. Through simulations H$_2$ molecule, we verify these improvements persist presence noise. This performed with IBM software noise models from real devices. also demonstrate how techniques can be...